1. Field of the Invention
The present invention is directed towards apparatus for bending sheet metal and, more particularly, is directed towards a power tool which is particularly adapted to bend the edge of sheet metal preparatory to forming a duct work joint.
2. Description of the Prior Art
A multitude of techniques and machines have been proposed and are known for bending sheet metal. In particular, the prior art suggests many devices and machines for bending sheet metal edges preparatory to the formation of what is known in the art as a Pittsburgh lock that is utilized extensively in the formation of air conditioning duct work and the like.
Prior art United States patents in this general art area of which we are aware include: U.S. Pat. Nos. 2,609,028; 2,660,909; 2,877,820; 3,188,729; 3,421,356; 3,477,272; 3,680,346; 3,015,293; 3,636,903; and 3,987,740.
By way of example, U.S. Pat. No. 3,680,346 illustrates a hand tool for rolling over and crimping the edge of an aluminum foil cover about the edge of a container, while U.S. Pat. No. 2,660,909 illustrates a pivoted sheet metal flanging hand tool.
U.S. Pat. No. 3,421,356 teaches a tool for crimping an upstanding flange on one panel about the edge of another overlying panel, while U.S. Pat. No. 3,477,272 shows a similar type device.
However, each of the prior art devices suffer from one or more deficiencies. More particularly, we have found that the prior art devices are extremely difficult to utilize when it is necessary to bend the edge of a curved piece of sheet metal. Most of the prior art machines are bulky, expensive and relatively complex, and are not adapted to be portable nor easily used. Their general bulkiness and complexity do not lend themselves to ease of use with curved edges of sheet metal which are frequently encountered and are necessary to be utilized in many air conditioning duct work installations.
It would therefore be extremely advantageous if apparatus were provided which is inexpensive, easy to utilize with existing power tools, and which permits rapid and easy bending of sheet metal edges, especially curved sheet metal edges.